s = input("请输入一个字符串（只能包括字母、数字、空格）:")
res = True
if s.isspace() is False:
    a_01 = s.replace(' ','')
    # print(a_01)
    a_02 = a_01.lower()
    # print(a_02)
    if a_02.isalnum() is False:
        print("含有非法字符，验证失败！！！")
    else:
        begin = 0
        end = len(a_02) -1
        while begin < end:
            if a_02[begin] != a_02[end]:
                res = False
                break
            begin += 1
            end -= 1
        print(res)
else:
    print(res)